To me personally, it is not monolith vs microservice that bothers me, but statefull vs stateless services.

If a service can't assume local state, it creates unnecessary design overhead. For example, you cannot achieve exactly-once semantics between two services without local-state. If you replace local-state with message-queues, you just turned 1-network-1-disk op into 5-network-3-disk op and introduced loads of other problems.